Display device

ABSTRACT

The liquid crystal display device according to this invention realizes three-dimensional picture images without using lenticular lenses etc. In addition, this liquid crystal display device has a transparent picture screen so that remote display picture images or three-dimensional picture images of high luminance are seen multiplexed with the background. The display device is constructed by arranging picture elements in which volume-phase type holograms are formed by a periodical construction of liquid crystals and polymers. Diffraction light from first picture element groups which are distributed uniformly reaches a left eye of an observer while diffraction light from second picture element groups which are distributed uniformly reaches a right eye of an observer. The condition of the picture elements are switched to diffract irradiated light or to transmit the light, thus a desired picture image comprising a dot matrix can be displayed. The first picture element groups display parallax picture for the left eye, and the second picture element groups display parallax picture for the right eye.

This application is a Divisional of application Ser. No. 08/989,579,filed Dec. 12, 1997, now U.S. Pat. No. 5,864,375, which is a Divisionalof application Ser. No. 08/603,036, filed Feb. 16, 1996, now U.S. Pat.No. 5,731,853, which application(s) are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to a display device which enablesthree-dimensional picture display using a polymer-dispersed type liquidcrystal.

BACKGROUND OF THE INVENTION

A polymer-dispersed type liquid crystal display device disperses liquidcrystals into polymers and uses the scattered light. This liquid crystaldisplay device does not need a polarizing plate so it can provide aclearer picture compared to a TN type liquid crystal display device.Therefore, the polymer-dispersed type liquid crystal display device hasbeen actively developed. FIG. 13 shows an example of a conventionalpolymer-dispersed type liquid crystal display device. In this drawing,51 is a polymer-dispersed liquid crystal (PDLC) layer, 52 is atransparent substrate, 53 and 54 are transparent electrodes, 55 is aphoto-absorbing plate, and 56 is a color filter.

The liquid crystals dispersed into the polymer base material arearranged disorderly, or they are in a scattered state. When voltage isapplied between the pair of transparent electrodes (53, 54) which faceeach other across the PDLC layer 51, the liquid crystals become orderly,namely transparent. The process can be reversed. The transparentelectrodes 53 and 54 are constructed to have picture elements formed onthe transparent substrate 52.

The liquid crystal display device displays pictures using external lightlike natural light or indoor light. The light beam entering through acolor filter 56 passes the PDLC layer 51 and is absorbed by thephoto-absorbing plate 55 when the picture elements are transparent. So,the observer sees the light as black. The light that enters thescattered picture elements (the shaded portion) is partly scattered, andpasses the color filter 56 again to outgo at a wide angle. So theobserver sees it as colored light.

FIG. 14 shows another well-known example of a conventionalthree-dimensional (3-D) picture display device, in which a lenticularlens 57 and a display device 58 are combined. The lenticular lens 57 isconstructed by arranging a number of long and narrow cylindrical lenses.The lenticular lens is disposed in front of the display device 58 like aCRT or a liquid crystal display.

The picture image shown in the display device 58 is divided into pairsof frames arranged alternately in a stripe pattern. The plain-coloredstripes constitute first frames 59 while the shaded stripes constitutesecond frames 60.

When the first frames 59 display a parallax picture for a right eye andthe second frames 60 display a parallax picture for a left eye, theparallax picture for the left eye is caught only by the left eye of anobserver at a predetermined position, while the parallax picture for theright eye is caught only by the right eye of the observer, due to thefunction of the lenticular lens. For the observer 61, the picture imageseems to appear on the display screen like a 3-D picture.

However, such a conventional liquid crystal display device only providesa picture with inferior luminance because of the following reason. Asshown in FIG. 15, the light beam enters, passes the PDLC layer, andforms scattered light. This is generally known as front scattering. Backscattering is a scattering to the back side (incident side). In a PDLClayer, back scattering never exceeds front scattering. According to theconventional technique, more than half of the light which entersscattering picture elements is absorbed by the photo-absorbing plate 55.Therefore, the luminance of the picture is always low, and it isdifficult to constitute a direct-view display.

In addition, the PDLC layer 51 and the transparent electrodes (53, 54)are sandwiched by the photo-absorbing plate 55 and the color filter 56.Even if the PDLC layer 51 becomes transparent because of voltageapplication, this property cannot be fully utilized. Further, it isimpossible to display 3-D pictures with the conventional structure. The3-D picture display device in FIG. 14 needs a lenticular lens, so thedevice cannot provide a transparent display picture.

SUMMARY OF THE INVENTION

The object of this invention is to provide a display device whichenables a 3-D picture display without using a lenticular lens etc., abright direct-view display device, a display device having a transparentpicture display part, and further a display device that enables colordisplay.

In order to obtain these advantages, a first display device of thisinvention has electrode layers inside two substrates which are facingeach other, and a light-modulating layer between these electrode layers.The light-modulating layer comprises liquid crystal phases and polymerphases distributed as holograms. At least one of the two pairs ofsubstrates and electrode layers is transparent. The electrode layers arepatterned so that picture elements arranged in a matrix are formed. Thelight-modulating layer sandwiched between the electrode layers comprisesfirst picture element groups and second picture element groupsdistributed almost uniformly in stripe or in mosaic form. On each of thepicture elements of the first groups, a hologram is formed to diffractthe irradiated light beams in the direction of the observer's left eye.On each of the picture elements of the second groups, another hologramis formed to diffract the irradiated light beams in the direction of theobserver's right eye.

According to the first embodiment of this invention, the voltage appliedto the electrode layers is controlled for every picture element, and aparallax picture for a left eye is displayed on the first pictureelement groups while a parallax picture for a right eye is displayed onthe second picture element groups. Thus a 3-D picture display isrealized without lenticular lens etc. If the two pairs of substrates andelectrode layers are transparent and a light beam is irradiated frombehind at a predetermined incident angle, a display device with highluminance, which has a transparent picture display part and whichenables to multiplex a displayed picture at the back, will be realized.

According to a second embodiment of this invention, the first pictureelement groups comprise hologram picture elements of red, blue and greenwhich are distributed substantially uniformly. The hologram pictureelements diffract the irradiated light beams of red, blue or green andturn them to the observer's left eye. The second picture element groupscomprise hologram picture elements of red, blue and green which aredistributed substantially uniformly. The hologram picture elementsdiffract the irradiated light beams of red, blue or green and turn themto the observer's right eye. For example, hologram picture elements ofred, blue and green are repeatedly arranged by turns in the longitudinaldirection of each picture element group arranged in stripe form. As aresult, a color display will be realized.

According to a third embodiment of the invention, plural holograms areformed in multiplex on each of the picture elements of the first pictureelement groups. The holograms diffract the irradiated light beam andturn it to left eyes of plural observers at different positions. Pluralholograms are formed in multiplex on each of the picture elements of thesecond picture element groups. The holograms diffract the irradiatedlight beam and turn it to right eyes of plural observers at differentpositions.

According to this embodiment, it is possible to provide the same 3-Dpicture for plural observers. Similar to the above-mentioned embodiment,a color display will be realized by distributing hologram pictureelements of red, blue and green substantially uniformly on each of thepicture element groups.

A fourth display device of this invention has electrode layers insidetwo substrates which are facing each other, and a light-modulating layerbetween these electrode layers. The light-modulating layer comprisesliquid crystal phases and polymer phases distributed as holograms. Atleast one of the two pairs of substrates and electrode layers aretransparent. The electrode layers are patterned so that picture elementsarranged in a matrix are formed. The light-modulating layer sandwichedbetween the electrode layers comprises picture element groups of 2 nkinds which are distributed substantially uniformly in stripe or inmosaic form, where n is a natural number bigger than 1. When k equals nor a natural number smaller than n, a hologram is formed on each of thepicture elements composing the k-th picture element group. The hologramdiffracts the irradiated light beam and turns it to the observer's lefteye. On each of the picture elements composing the (k+n)-th pictureelement group, a hologram is formed to diffract the irradiated lightbeam and turn it to the observer's right eye.

According to this embodiment, it is possible to provide not only anindependent picture (the same picture) but also different pictures forplural observers at different positions. A color display will berealized by distributing hologram picture elements of red, blue andgreen substantially uniformly on each of the picture element groups.

In the above-mentioned embodiments, a hologram is formed on each of thepicture elements so that the diffraction light has a horizontal spreadwithin a predetermined angle. Then, an observer can see a requestedpicture even if his position is shifted to the right or left to somedegree. In addition, the position of the observer can be shiftedvertically as well as horizontally to some degree if a hologram isformed, and its diffraction has a predetermined emission angle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the construction of the display device relating to Example1 of this invention.

FIG. 2 shows the function of a picture element composing the firstpicture element groups of the display device of FIG. 1.

FIG. 3 shows the function of a picture element composing the secondpicture element group of the display device of FIG. 1.

FIG. 4A shows the construction of every picture element of the displaydevice of FIG. 1 in minute detail when voltage is not applied. And FIG.4B shows the same construction when voltage is applied.

FIG. 5 is a perspective view to show the relation between the irradiatedlight and the diffraction light according to the display device of FIG.1.

FIG. 6(A) is a side view to indicate the method of forming the displaydevice of FIG. 1, in which the first picture element groups and thesecond picture element groups are formed alternately in stripes, andFIG. 6(B) is a plan view to indicate the same method.

FIG. 7 indicates how the experiment is carried out using the displaydevice of FIG. 1.

FIGS. 8A, 8B and 8C are side views to show other examples according tothe light source for the display device of FIG. 1. FIG. 8A is a basicconstruction in which a light source is disposed behind the displaydevice. FIG. 8B is a variation in which a light source is disposed infront of the display device. And FIG. 8C is another variation in whichindoor light or natural light is used for the light source.

FIG. 9 is a perspective view of a variation of the display device ofFIG. 1, in which hologram patterns of a stabilized picture image arewritten on the light-modulating layer of the display device.

FIG. 10 is a perspective view to show the construction of the displaydevice relating to Example 2 of this invention.

FIG. 11 is a perspective view to show the relation between the pictureelement groups and the observers according to FIG. 10.

FIG. 12 is a perspective view to show the relation between the pictureelement groups and the observers according to Example 3 of theinvention.

FIG. 13 is a cross-sectional view of a conventional polymer-dispersedtype liquid crystal display device.

FIG. 14 is a perspective view of a conventional three-dimensionalpicture image display device.

FIG. 15 shows the light scattering according to a conventionalpolymer-dispersed type liquid crystal display device.

DETAILED DESCRIPTION OF THE INVENTION

A preferable embodiment is explained below referring to some Examplesand drawings.

EXAMPLE 1

FIG. 1 shows the construction of a display device of the firstembodiment of this invention. In FIG. 1, numerals 1 and 2 aretransparent glass substrates, and 3 and 4 are transparent electrodelayers. Numeral 5 is a light-modulating layer that comprises firstpicture element groups 6 and second picture element groups 7 arrangedalternately in stripes. In FIG. 1, the picture element groups 6 comprisepicture elements 8 arranged vertically, while the picture element groups7 comprise picture elements 9 arranged vertically. The picture element 8is indicated as a plain cell, and the picture element 9, as a shadedcell. Numeral 10 is a light source and light beam 11 is irradiated fromthe backside of the transparent glass substrate 2. For the sake ofconvenience, the light-modulating layer 5 is drawn separated from theelectrode layer 3, though actually, the two layers are adhered to eachother.

FIG. 2 shows the simplified typical construction of the picture element8 composing the picture element group 6. The picture element 8 has aperiodical construction in which polymer phases 12 and liquid crystalphases 13 are alternately formed. The pitch is about 0.3 micron, and thethickness of the picture element is about 10 microns. The direction ofthe periodical construction, or grating vector 14, inclines 0.28° towardthe left side and about 34.7° downward from the normal line of thepicture element surface.

The picture element 9 composing the picture element groups 7 also has aperiodical construction as shown in FIG. 3. The direction of the typicalperiodical construction, or grating vector 15, inclines about 34.7°downward and about 0.28° to the right side.

The periodical constitution is made by the following steps:

mixing photosensitive monomers and/or oligomers, a nematic liquidcrystal, a polymerization initiator and a sensitizer to prepare aprecursor;

sandwiching the precursor between the electrode layers (3, 4) inside theglass substrates (1, 2);

writing patterns by irradiating interference patterns formed by an argonlaser of 515 nm; and

polymerizing the entire surface by irradiating ultraviolet ray by alow-pressure mercury vapor lamp.

A ethylenic unsaturated monomer which is liquid or has a low meltingpoint, especially acrylic or methacrylic esters, is suitable for makinga light-modulating layer by photo-polymerization. These monomers may bepolyfunctional monomers like trimethylpropane triacrylate, or oligomerslike poly(ethylene glycol)diacrylate and urethane acrylate. These can beused individually or in combination. Moreover, other monomers likestyrene or carbazole can be used if necessary.

These monomers and oligomers are not particularly limited. An expert mayselectively use well-known monomers and oligomers like those used formaking a polymer-dispersed type liquid crystal, or aphoto-polymerization composition for making a volume hologram describedin Japanese Laid Open (Tokkai-Hei) No. 2-3082. In conductingphoto-polymerization by coherent light, a sensitizing dye suitable tothe wavelength, and appropriate photopolymerizing initiator etc. areneeded. This can be selected from a lot of combinations like cyaninedyes, dyes of cyclopentanone, diphenyl iodonium salt, or the combinationof diphenyl iodonium salt and dyes, quinones, triphenyl imidazole dinerand hydrogen donor. A liquid crystal having a larger birefringence anddielectric anisotrophy and a smaller elastic constant is suitable forthe purpose. Such a liquid crystal can be selected from commerciallyavailable liquid crystals.

The function of the picture elements 8 and 9 is explained referring toFIGS. 4A and 4B. In these figures, a picture element like 8 or 9 whichhas a periodical construction is shown comprehrensively. In FIG. 4A,polymer phases 12 are expressed by inclined straight lines and liquidcrystal phases 13 between the lines are phase-separated in a repeatingpattern.

In the liquid crystal phases 13, liquid crystal molecules gather andform liquid crystal droplets 18. These liquid crystal droplets 18 aredispersed randomly and oriented in random directions. The averagerefractive index of the liquid crystal phases 13, which is equivalentlydefined, is bigger (e.g. 1.56) than that of the polymer phases 12 (e.g.1.5).

The periodical construction formed by the polymer phases 12 and theliquid crystal phases 13 having different refractive indexes forms ahologram of the volume phase type. Accordingly, the incident light 16,which enters at a predetermined Bragg angle as shown in FIG. 4, istransformed to the diffracted light 17 with an extremely small loss,then efficiently reaches the eyes of an observer 19.

When a voltage is applied between the electrode layers (3,4) sandwichingthe light-modulating layer 5 as shown in FIG. 4B, the liquid crystaldroplets 18 in the liquid crystal phases 13 are oriented in thedirection of the electric field. As a result, the difference ofrefractive indexes of the polymer phases 12 and the liquid crystalphases 13 is lost, and the power to diffract the light of thelight-modulating layer 5 is lost. As a result, the incident light 16passes through the light-modulating layer 5 and becomes transmittedlight 20. Therefore, the light beam does not reach the eyes of theobserver 19. For the observer 19, the display device containing thelight-modulating layer 5 and the transparent electrode layers (3, 4)looks transparent.

In this Example, the diffraction efficiency of each picture element isover 70%. In an experiment, a halogen lamp was used for the light source10. In this experiment, the luminance of the display screen was as muchas 2000 cd/m². The directivity of the diffracted light was so high thatit was not observed from a position out of the course of the light. Inother words, the display device seemed transparent when the observer 19was not at the position shown in FIG. 4A. When an alternating currentvoltage of 100V was applied between the electrode layers 3 and 4, theluminance of the display screen was lowered to 100 cd/m² or less.

When irradiated light 11 enters from behind the above-mentioned pictureelements (8, 9) at an incident angle of about 60°, the light 21 which isdiffracted by the picture element 8 and which outgoes from the front(turning to the observer) will outgo in the direction which ishorizontal and inclines about 0.85° to the left from the observer'sposition as shown in FIG. 5. Similarly, the light 22 which is diffractedby the picture element 9 and which outgoes from the front will outgo inthe direction which is horizontal and inclines about 0.85° to the rightfrom the observer's position. As a result, if the observer is at apredetermined position, only the light beam 21 reaches the left eye, andonly the light beam 22 reaches the right eye. This is peculiarly causeddue to the angular selectivity of a thick hologram.

As mentioned above, the picture elements 8 and 9 are typical ones of thepicture element groups 6 or 7. There is a little difference between theadjacent picture elements composing the picture element groups 6 or 7.Because of the variation, the diffraction light beam from the pictureelement groups 6 reaches the left eye of the observer, while thediffraction light beam from the picture element group 7 reaches theright eye.

In this hologram, picture element groups (6, 7) are arranged alternatelyin stripes so as to correspond to each of the eyes of the observer. Thehologram in FIG. 6 can be made by using a mask plate MK in which slitsof d width are arranged at every other position as shown in FIG. 6. Thewidth (d) is equivalent to the width of one stripe. As shown in the sideview of FIG. 6A and the plan view of FIG. 6B, object light OL isirradiated to fully spread in the display device 23 through a pair ofconcave lenses disposed at the position corresponding to both eyes of anobserver located a predetermined distance from the front of the displaydevice 23. At the same time, reference light RL is irradiated in thedirection of the incident angle of 60° to the display device 23, and theinterference patterns of the light beams are written on thelight-modulating layer of the display device 23.

During this operation, the mask plate MK is disposed in front of thedisplay device 23 as shown in FIG. 6B so that the direction of the slitsbecomes vertical. Then, only the object light OL for the left eye isirradiated. With this operation, the interference pattern for the lefteye is written and the first picture element groups 6 are formed instripes. Next, the mask plate MK is horizontally shifted by the width ofthe stripe (width of the slit) d, and the object light OL for the righteye is irradiated. With this operation, the interference pattern for theright eye is written, and the second picture element groups 7 are formedin stripes.

As shown in FIG. 1, the display device of this example has alight-modulating layer 5 sandwiched between the transparent electrodelayers (3, 4) inside the transparent glass electrodes (1, 2). Thisconstruction is basically the same as a normal transmittance type liquidcrystal display device. Each of the transparent electrode layers (3, 4)is patterned to constitute picture elements arranged in a matrix. Inother words, the voltage applied between the transparent electrodelayers (3, 4) of picture elements can be controlled independently. Thus,a desired picture image comprising a dot matrix can be displayed. Here,the term "display of picture image" means that voltage is not appliedbetween the electrodes of the picture element composing the pictureimage, and the diffraction light of the picture image reaches theobserver. Since voltage is applied to the other picture elements, theother picture elements are transparent, and the observer can see thebackground of the display device.

A simple experiment was conducted using such a display device. As shownin FIG. 7, numeral "8" is displayed on the first picture element groups6 for the left eye (plain portions) and on the second picture elementgroups 7 for the right eye (shaded portions) respectively, shifted alittle side to side. In FIG. 7, the picture image 24 displayed on thefirst picture element groups 6 is indicated with white dots while thepicture image 25 displayed on the second picture element groups 7 isindicated with black dots.

The display device 23 was set separated from the observer 19 by 50 cm,and illuminated from behind at an incident angle of 60°. When theobserver 19 saw the display device 23, the letter "8" appeared on theposition behind the display device 23. The position was two meters awayfrom the observer.

During the illumination, the other parts which do not display thenumeral are transparent. Therefore, the "8" appearing on the picturescreen seems overlapping with the backgrounds which is two meters awayfrom the observer. In this example, the part to display the pictureimage is transparent, so the displayed picture image is multiplexed withthe background of the display device and looks three-dimensional. Suchan effect cannot be found from any other inventions of the field.Applying this technique, a remote focusing function of a head-up displayof an automobile etc. can be realized.

The position where the image "8" appears, namely the distance from theobserver will be decided geometrically depending on the interval of theshift between the image for the left eye displayed on the first pictureelement groups 6 and the image for the right eye displayed on the secondpicture element groups 7. It is clear from FIG. 7 that more and moreseparated, the two picture images seem to be appearing farther from theobserver. If the image for the left eye and that for the right eye areshifted in the reverse direction, the picture image appears in front ofthe display device 23.

Instead of the letter "8", a three-dimensional object will be taken asan example. A pair of picture images which are a little differentaccording to parallax of both eyes seeing the object is displayed on thepicture element groups 6 and 7 respectively. Then the object appearsthree-dimensionally when the observer 19 sees the display device 23. Inother words, a three-dimensional display device can be constituted usingparallax without any lenticular lens or other means of conventionaltechnique. When the same picture image is displayed on the pictureelement groups 6 and 7, instead of displaying different images accordingto the parallax, a three-dimensional picture cannot be obtained, but apicture image of high luminance may be obtained. The picture image seemsto appear overlapping the background.

In this example, the light source 10 is disposed behind the displaydevice 26, as shown in the side view of FIG. 8A, so the diffractionlight passing through the display device 26 reaches the eyes of theobserver. Or, according to FIG. 8B, the light source can be disposed infront of the display device 26 so that the diffraction light reflectedby the display device 26 reaches the eyes of the observer. As shown inFIG. 8C, indoor light or natural light also can be used, if anyspecialized light sources are not provided. In this case, thetransmitted diffraction light or the reflected diffraction light reachesthe eyes of the observer. If the reflected diffraction light from thelight source in front of the display device 26 reaches the observer, thesubstrate of the back-side and the electrode are not necessarilytransparent.

The hologram picture element is formed so that the diffraction lightfrom the picture element has been horizontally spread within apredetermined angle. Therefore, the observer can see a predeterminedpicture image even if his position is shifted a little to the left or tothe right. In addition, the hologram picture element is constituted tobe spread vertically within a predetermined angle, so that thediffraction light from the hologram picture element has an emissionangle within a predetermined angle. Thus, the observer can see apredetermined picture image even if his position is shifted to somedegree vertically and horizontally.

In this example, the first picture element groups 6 and the secondpicture element groups 7 comprise hologram picture elements of red, blueand green that are distributed substantially uniformly. The hologrampicture elements respectively diffract the light beams of red, blue andgreen and turn them to the left or right eye of the observer. As aresult, color display is realized.

Generally, hologram picture elements of red, blue and green arerepeatedly arranged by turns to be distributed substantially uniformlyin the vertical direction of the picture element groups (6, 7). Such aconstruction can be realized by using a mask plate following the methodshown in FIG. 6. However, the mask plate is different from the maskplate MK in that apertures are formed horizontally in every otherposition and vertically in every third position in a matrix state. Here,an aperture corresponds to a picture element.

The object light and the reference light of red, blue and green areirradiated by turns, while shifting this mask plate vertically. As aresult, picture element groups in which the hologram picture elements ofred, blue and green are repeatedly arranged by turns are obtained.Therefore, the first picture element groups are formed by writing thehologram patterns three times while shifting the mask vertically. Thesecond picture element groups are formed by writing the hologrampatterns three times while shifting the mask horizontally. As a result,the display device which enables three-dimensional display and colordisplay is manufactured by writing the hologram patterns six times,though the method is not limited to this example.

The precondition of this example is that a desired picture imagecomposed of a dot matrix is displayed on a display device by controllingthe voltage applied between the electrode layers sandwiching thelight-modulating layer for every picture element. It is also possiblethat a still picture image is written as a hologram pattern on alight-modulating layer of a display device 28. In FIG. 9, two hologrampatterns (29, 30) displaying numeral "8" are written at the positionshifted to the left and right. The first hologram pattern 29 turns thediffraction light to the left eye of the observer while the secondhologram pattern 30 turns the diffraction light to the right eye of theobserver. Such hologram patterns are formed by writing the interferencepattern on the light-modulating layer of the display device 28. Theinterference pattern comprises the object light and the reference lightwhich contain picture information like reflected light or transmittedlight of an object.

Even in the still picture display, it is possible to controlmultiplexing of a picture image in the background when an observer seesthe display device 28. For this purpose, the voltage applied between theelectrode layer is controlled as a whole, or for every picture element.

EXAMPLE 2

In Example 1, the display device is constituted on the condition thatonly one observer exists. According to Example 2 described below, pluralobservers can see the same picture. This example will be explainedaccording to the construction of the picture elements that are differentfrom those of Example 1.

FIG. 10 indicates how the picture elements (31, 32) composing thedisplay device of this example functions. These picture elements 31 and32 are called multiplexed hologram picture elements to diffract anincident light beam from a direction to plural directions. Numeral 31 isa multiplexed hologram picture element for left eye, which turns thediffraction light to the left eyes of plural observers. Numeral 32 is amultiplexed hologram picture element for the right eye, which turns thediffraction light to right eyes of plural observers.

These multiplexed holograms are formed by multiplexing pairs ofperiodical construction of polymer phases 12 and liquid crystal phases13 in the same cell. As mentioned in Example 1, a multiplexed hologrampicture element is formed by:

sandwiching a precursor comprising photosensitive monomers (oligomers),nematic liquid crystal, polymerization initiator, sensitizer etc.,between the glass substrates (1, 2) and the electric layers (3, 4);

irradiating an interference pattern formed by an argon laser of 515 nmto write patterns; and

irradiating an ultraviolet light by a low-pressure mercury vapor lamp topolymerize the whole plate. During the writing step, different patternsare written by turns. More specifically, several patterns are written byturns while shifting the position of a pair of concave lenses accordingto the positions of observers. The lenses correspond to the left andright eyes. Such an operation is conducted when picture element groupswhich are arranged alternately like stripes are formed to correspond toboth eyes, in a method using the mask plate MK of FIG. 6. Multiplexedhologram picture elements 31 and 32 are manufactured in this way.

The picture element 31 creates diffraction light for the left eye (33)in the different directions of n kinds to the light beam 11. The pictureelement 32 creates diffraction light for the right eye (34) in thedifferent directions of n kinds to the light beam 11. And the i-thdiffraction light beams 35 and 36 of the diffraction light beams forleft and right eyes (32, 34) reach the left and right eyes of oneobserver.

FIG. 11 shows the i-th and (i+1)-th diffraction display light beams toindicate the relation between a display device and observers more indetail. The light beams reach the first observer (37) and the secondobserver (38), respectively. In FIG. 11, the picture element groups forthe left eye (39) indicated with a plain stripe and the picture elementgroups for the right eye (40) indicated with a shaded stripe arearranged alternately. The picture element groups 39 are formed withmultiplexed hologram picture elements 31 of FIG. 10 arranged verticallywhile the picture element groups (40) are formed with multiplexedhologram picture elements 32 arranged vertically.

The i-th diffraction light 41 from the picture element groups 39 reachesthe left eye of the observer 37, and the (i+1)-th diffraction light 42reaches the left eye of the observer 38. Similarly, the i-th diffractionlight 43 from the picture element groups 40 reaches the right eye of theobserver 37, and the (i+1)-th diffraction light 44 reaches the right eyeof the observer 38. In this way, the same picture image is provided fortwo observers.

Similar to Example 1, a three-dimensional picture display can beprovided to the observers by displaying different picture images on thepicture element groups (39 and 40) to correspond to parallax picture ofboth eyes. In addition, a transparent display device having highluminance can be constituted by displaying the same picture imagewithout providing parallax for both eyes. Similarly, the othervariations like coloring described in Example 1 can be also applied tothis example.

EXAMPLE 3

The display device explained in Example 2 provides the same pictureimage for plural observers. It is also possible to realize a displaydevice to provide different picture images for plural observers. FIG. 12relates to a case that different picture images are provided for a firstobserver 45 and a second observer 46.

In FIG. 12, numeral 47 is the first picture element group to turn thediffraction light to the left eye of the first observer 45, 48 is thesecond picture element group to turn the diffraction light to the lefteye of the second observer 46, 49 is the third picture element group toturn the diffraction light to the right eye of the first observer 45,and 50 is the fourth picture element group to turn the diffraction lightto the right eye of the second observer 46. In this way, four kinds ofpicture element groups are repeatedly formed by turns.

According to this construction, it is possible to differentiate thepicture image formed by the picture element groups (47 and 49) from thatof the picture element groups (48 and 50). Accordingly, the twoobservers can see not only the same three-dimensional picture image butalso independent three-dimensional picture images, respectively.

In the construction, four kinds of picture element groups are repeatedlyformed by turns. In order to obtain this construction, hologram patternsare written four times, shifting a mask plate side-to-side. The maskplate having slits arranged at every four positions is used in place ofthe mask plate MK.

Generally, picture element groups of (2×n) kinds should be repeatedlyformed by turns in order to provide n kinds of independentthree-dimensional picture images for n number of observers. When k≦n,the diffraction light of the k-th picture element groups and those ofthe (k+n)-th picture element groups reach the left and right eyes of anobserver.

Similarly in this example, variations like coloring described in theExamples 1 and 2 can also be applicable.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiments disclosedin this application are to be considered in all respects as illustrativeand not restrictive, the scope of the invention is indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. A display device having a pair of electrodelayers inside a pair of opposed substrates, and a light-modulating layercomprising liquid crystal phases and polymer phases as holograms beingbetween the electrode layers;wherein at least one of the two pairs ofsubstrates and electrode layers is transparent, said electrode layersare patterned to form picture elements arranged in a matrix, saidlight-modulating layer comprises picture element groups of 2 n kindsdistributed substantially uniformly in stripes or in mosaic where n is anatural number more than one, and when k is a natural number less thanor equal to n, holograms are formed on each k-th picture element groupsso as to diffract irradiated light and turn it in a direction of lefteyes of observers while other holograms are formed on each (k+n)-thpicture element groups so as to diffract irradiated light and turn it ina direction of right eyes of observers, whereby independent pictureimages are provided for plural observers at different positions.
 2. Thedisplay device according to claim 1, wherein said k-th picture elementgroups display a parallax picture for the left eye and said (k+n)-thpicture element groups display a parallax picture for the right eyes. 3.The display device according to claim 1, wherein holograms are formed onevery picture element so that said diffraction light has a horizontalspread within a predetermined angle.
 4. The display device according toclaim 1, wherein holograms are formed on every picture element so thatsaid diffraction light has a predetermined emission angle.
 5. Thedisplay device according to claim 1, provided with a light source toradiate light which enters at least a predetermined incident angle frombehind or in front of a picture screen.
 6. A display device having apair of electrode layers inside a pair of opposed substrates, and alight-modulating layer comprising liquid crystal phases and polymerphases as holograms being between the electrode layers;wherein at leastone of the two pairs of substrates and electrode layers is transparent,said electrode layers are patterned to form picture elements arranged ina matrix, said light-modulating layer comprises picture element groupsof 2 n kinds distributed substantially uniformly in stripes or in mosaicwhere n is a natural number more than one, and when k is a naturalnumber less than or equal to n, holograms of red, blue and green areformed on each k-th picture element groups so as to diffract irradiatedlight beams of red, blue and green and turn them in a direction of lefteyes of observers while other holograms of red, blue and green areformed on each (k+n)-th picture element groups so as to diffractirradiated light beams of red, blue and green and turn them in adirection of right eyes of observers, whereby independent color pictureimages are provided for plural observers at different positions.
 7. Thedisplay device according to claim 6, wherein said k-th picture elementgroups display a parallax picture for the left eye and said (k+n)-thpicture element groups display a parallax picture for the right eyes. 8.The display device according to claim 6, wherein holograms are formed onevery picture element so that said diffraction light has a horizontalspread within a predetermined angle.
 9. The display device according toclaim 6, wherein holograms are formed on every picture element so thatsaid diffraction light has a predetermined emission angle.
 10. Thedisplay device according to claim 6, provided with a light source toradiate light which enters at least a predetermined incident angle frombehind or in front of a picture screen.